Portion of tractor



FIG. 1 is a top and left front perspective view of a portion of tractor, showing our design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a rear elevational view thereof;

FIG. 4 is a left side elevational view thereof;

FIG. 5 is a right side elevational view thereof; and,

FIG. 6 is a top plan view thereof.

All broken lines shown in the figures represent environmental structures and form no part of the claimed design. 

CLAIM The ornamental design for a portion of tractor, as shown and described. 